[1] On April 28 2001, simultaneous global images of electron and proton aurora were obtained by IMAGE- FUV following a sudden increase of solar wind dynamic pressure. The local time and intensity ... [more ▼]

[1] On April 28 2001, simultaneous global images of electron and proton aurora were obtained by IMAGE- FUV following a sudden increase of solar wind dynamic pressure. The local time and intensity distribution of both types of precipitation are examined and compared. It is found that the electron and the proton precipitation both start in the post noon sector and expand concurrently, but the expansion into the nightside starts sooner for the protons than for the electrons. The characteristic rise time in the onset sector is on the order of 6 minutes. A distinct dynamics and morphology of electron and proton precipitation is observed in the nightside sector. DMSP electron measurements in the afternoon sector indicate that the shock has a significant effect on the electron spectral characteristics. It is suggested that the various Alfven frequencies generated by the shock account for the two different speeds of propagation of the disturbance. [less ▲]

[1] The FUV instrument on the IMAGE spacecraft frequently observes intense ultraviolet (UV) emission from a localized dayside region poleward of the general auroral oval location. One type of these ... [more ▼]

[1] The FUV instrument on the IMAGE spacecraft frequently observes intense ultraviolet (UV) emission from a localized dayside region poleward of the general auroral oval location. One type of these emissions has been described as the signature of direct proton precipitation into the cusp after lobe reconnection during northward interplanetary magnetic field (IMF) and high solar wind dynamic pressure periods [Frey et al., 2002]. Here we describe a completely different type of high latitude aurora, which does not show any signature of precipitating protons. It also occurs during northward IMF conditions however, only during periods of very low solar wind dynamic pressure. It occurs at a much higher geomagnetic latitude than the normal cusp location and only during periods of positive IMF By. The intensity of the UV emission is somewhat anti-correlated with the solar wind dynamic pressure, much in contrast to the cusp emission. The brightness of the localized emission changes rapidly on time scales between 30 and 70 minutes without corresponding changes in solar wind properties. Coincident measurements by the FAST spacecraft verify that this is not the cusp, that ion precipitation is absent in these regions, and that strong precipitation of field-aligned accelerated electrons causes the aurora. We interpret this aurora as the optical signature of electron precipitation in the upward leg of a current system which closes the downward leg of the current system into the cusp in the ionosphere. [less ▲]

A wide variety of solar system bodies are now known to radiate in the soft X-ray energy (<5 keV) regime. These include planets (Earth, Jupiter, Venus, Saturn, Mars): bodies having thick atmospheres, with ... [more ▼]

A wide variety of solar system bodies are now known to radiate in the soft X-ray energy (<5 keV) regime. These include planets (Earth, Jupiter, Venus, Saturn, Mars): bodies having thick atmospheres, with or without intrinsic magnetic field; planetary satellites (Moon, Io, Europa, Ganymede): bodies with thin or no atmospheres; and comets and Io plasma torus: bodies having extended tenuous atmospheres. Several different mechanisms have been proposed to explain the generation of soft X-rays from these objects, whereas in the hard X-ray energy range (>10 keV) X-rays mainly result from the electron bremsstrahlung process. In this paper we present a brief review of the X-ray observations on each of the planetary bodies and discuss their characteristics and proposed source mechanisms. [less ▲]